Scientists from the Universities of Oslo and Liverpool found that alcohol - or ethanol - levels can soar to 50 milligrams per 100 millilitres in goldfish and their wild relatives, crucian carp.

This is just over half of the legal drink drive limit in the UK.

Dr Cathrine Elisabeth Fagernes, from the University of Oslo, said: "The ethanol production allows the crucian carp to be the only fish species surviving and exploiting these harsh environments, thereby avoiding competition and escaping predation by other fish species with which they normally interact in [more hospitable] waters."

Goldfish produce alcohol so they can survive at the bottom of frozen ponds, where there is little or no oxygen.

Normally, these conditions would be lethal for living organisms.

But the fish get around this by turning a dangerous chemical called lactic acid into alcohol and then emitting it through their gills.